This invention relates to a process for the preparation of N-vinyl-2-oxazolidinone.
N-vinyl-2-oxazolidinones are useful in the preparation of polymers and such polymers are useful as complexing agents for a wide range of phenolic compounds and dyes, and in the preparation of plastics. In addition, they are useful in coating compositions and in adhesives and are valuable intermediates for dye-stuffs, dye receptors and textile assistants.
There are several known methods for the preparation of N-vinyl-2-oxazolidinone.
Arend et al., German Pat. No. 972,304, teach a three-step synthesis in which the last step comprises the dehydrochlorination of N-(2-chloroethyl)-2-oxazolidinone in the presence of Na.sub.2 O. Dreschel, J. Org. Chem., 22, 849 (1957), teaches a three-step preparation of N-vinyl-2-oxazolidinone in which the last step comprises dehydrochlorination of N-(2-chloroethyl)-2-oxazolidinone in the presence of potassium t-butoxide. These dehydrochlorination processes are disadvantageous because they involve a multistep synthesis of N-vinyl-2-oxazolidinone and the yields are poor.
Kutner, J. Org. Chem., 26, 3465 (1961), discloses a three-step synthesis of N-vinyl-2-oxazolidinone in which the last step comprises the pyrolysis of N-(2-acetoxyethyl)-2-oxazolidinone at a temperature of 580.degree. C. These conditions are very severe, and the oxazolidinone ring is susceptible to decomposition under such conditions.
Bakke, U.S. Pat. No. 3,033,829, discloses a process in which 2-oxazolidinone is transvinylated with a vinyl ether in the presence of a mercury catalyst to prepare a N-vinyl-2-oxazolidinone. This process involves the preparation of large amounts of acetal as a by-product along with the reduction of some of the mercury catalyst to elemental mercury which creates environmental problems.
Bakke, U.S. Pat. No. 2,905,690, discloses the preparation of N-vinyl-2-oxazolidinone by the Reppe synthesis. In particular, a 2-oxazolidinone is converted to its sodium salt by treatment with metallic sodium which is then vinylated with acetylene. This process is disadvantageous because it requires the use of high pressure and acetylene which creates a risk of explosion.
Ingleby, U.S. Pat. No. 3,346,586, discloses that the condensation product of 1 mole of an aldehyde and two moles of a 2-oxazolidinone can be decomposed to prepare one mole of N-vinyl-2-oxazolidinone and one mole of 2-oxazolidinone. The process involves heating the condensation product at reduced pressure, optionally in the presence of an acid catalyst. This process suffers from the disadvantage that low yields of the desired N-vinyl-2-oxazolidinone are achieved. In particular, it takes at least two moles of 2-oxazolidinone to prepare one mole of N-vinyl-2-oxazolidinone.
Seneokor et al., Khim. Geterotsikl Soedin, 275-7 (1970), teach that N-vinyl-2-oxazolidinone can be prepared by reacting vinylisocyanate with alkylene oxides. The instability and low availability of vinylisocyanate renders this process disadvantageous.
Prior to the invention disclosed herein, the skilled artisan was confronted with several problems in the preparation of N-vinyl-2-oxazolidinone. The formation of a N,N'-alkylidene-bis(2-oxazolidinone) under certain conditions is one such problem. Under acidic conditions, the N-vinyl-2-oxazolidinone undergoes decomposition to the starting 2-oxazolidinone. Further, 2-hydroxyethyl-2-oxazolidinone, an intermediate in the preparation of N-vinyl-2-oxazolidinone, is not thermally stable and undergoes decomposition. The prior art processes described herein often result in low yields of the desired product.
What is needed is a process for the preparation of N-vinyl-2-oxazolidinones in which the formation of the N,N'-alkylidene-bis(2-oxazolidinones) is prevented or minimized, and the decomposition of the product is prevented. What is further needed is a process in which no by-products are prepared which create environmental problems or create a danger of explosion. What is also needed is a reasonably simple process in which high yields of product can be achieved.